1. Field of the Present Invention
The present invention relates generally to electromagnetic tomography, and, in particular but not exclusively, to electromagnetic tomographic imaging with man-portable components, including methods, devices, and systems.
2. Background
Electromagnetic tomography (EMT) is a relatively recent imaging modality with great potential for biomedical applications, including a non-invasive assessment of functional and pathological conditions of biological tissues. Using EMT, biological tissues are differentiated and, consequentially, can be imaged based on the differences in tissue dielectric properties. The dependence of tissue dielectric properties from its various functional and pathological conditions, such as blood and oxygen contents, ischemia and infarction malignancies has been demonstrated.
Two-dimensional (2D), three-dimensional (3D) and even “four-dimensional” (4D) EMT systems and methods of image reconstruction have been developed over the last decade or more. Feasibility of the technology for various biomedical applications has been demonstrated, for example, for cardiac imaging and extremities imaging.
As in any biomedical imaging, the classical EMT imaging scenario consists of cycles of measurements of complex signals, as scattered or “interferenced” by a biologic object under study, obtained from a plurality of transmitters located at various points around the object and measured on a plurality of receivers located at various points around the object. This is illustrated in FIG. 1. As recounted elsewhere herein, the measured matrix of scattered EM signals may then be used in image reconstruction methods in order to reconstruct a 2D or 3D distribution of dielectric properties of the object, i.e., to construct a 2D or 3D image of the object. Still further, 4D imaging may be achieved by reconstructing 3D images at different time points.
Generally, it is very important for image reconstruction to precisely describe a distribution of EM field with an imaging domain 21. The distribution of EM field with an imaging chamber is a very complex phenomenon, even when there is no object of interest inside.
FIG. 2 is a schematic view of one possible embodiment of a prior art EM field tomographic spectroscopic system 10. Such a system 10 could carry out functional imaging of biological tissues and could also be used for a non-invasive mapping of electrical excitation of biological tissues 19 using a sensitive (contrast) material (solution or nanoparticles) injected into the biological tissue 19 or in circulation system, characterized by having dielectric properties that are a function of electrical field, generated by biological excited tissue 19. As illustrated in FIG. 2, the system 10 included a working or imaging chamber 12, a plurality of “EM field source-detector” clusters 26, an equal number of intermediate frequency (“IF”) detector clusters 28, and a control system (not shown). Although only two EM field source-detector clusters 26 and two IF detector clusters 28 are shown, a much larger number of each are actually used.
The imaging chamber 12 was a closed domain, such as a watertight vessel, of sufficient size to accommodate a human body or one or more parts of a human body. For example, the imaging chamber 12 may be a helmet-like imaging chamber to image brain disorders (for example acute and chronic stroke), ii) a cylindrical type chamber for extremities imaging, or iii) a specifically shaped imaging chamber for detection of breast cancer. As a result, the imaging chamber may have different shapes and sizes.
The imaging chamber 12 and its EM field clusters 26, as well as the IF detector clusters 28, have sometimes been mounted on carts in order to permit the respective components to be moved if necessary, and the carts may then be locked in place to provide stability.
Oversimplified, the system 10 operates as follows. An object of interest (e.g., biological tissue) is placed in the imaging domain 21. The transmitting hardware generates electromagnetic (EM) radiation and directs it to one of antennas. This antenna transmits electromagnetic waves into imaging domain 21, and all of the other antennas receive electromagnetic waves that have passed through some portion of the imaging domain 21. The receiving hardware detects the resulting signal(s), and then the same cycle is repeated for the next antenna and the next one until all antennas have served as a transmitter. As described, for example, in the aforementioned U.S. Pat. No. 7,239,731, code-division technology can be utilized such that the transmitting hardware generates EM radiation and directs it to a plurality of simultaneously transmitting antennas that are specifically coded by a unique “antenna specific code,” so that the source of the resulting EM radiation received at a particular receiving antenna can be “recognized” on the basis of the codes. The end result is a matrix of complex data which is transmitted to one or more computers in the control system that process the data to produce an image of the object 19 in the imaging domain 21. An algorithm called an “inversion” algorithm is utilized in this process.
FIG. 4 is a schematic illustration of a three-dimensional setting for the system of FIG. 2.
Unfortunately, traditional EMT technologies, while producing very useful results, have required equipment that is physically cumbersome and difficult to use. This can be true both for the technician, diagnostician, or the like as well as the person or animal who is being studied. With regard to latter, the discomfort caused by the imaging chamber can also be significant. The size and weight of the equipment also makes it very difficult to use the equipment in the place where it is assembled; disassembling and moving the equipment is not very feasible. Finally, the use of arrays of antenna and other equipment creates significant complexity and cost. Thus, a need exists for technology that produces similar results but in a cheaper, more convenient, and more comfortable physical form.
Moreover, a need exists for the imaging and diagnostic capabilities offered by EMT technologies to be available in settings beyond the traditional clinic setting. In particular, a need exists for EMT technologies to be available in everyday human life, providing safe, on-demand, on-line (real time) screening and diagnosis.